Sequential detection ion chromatography

Abstract

Packings or equivalent structures which produce radial mixing in channels can be used to enhance reagent addition devices for ion chromatography post column reactions in which band spreading at detrimental levels is effectively controlled. Application to two dimensional conductometric detection in simultaneous suppressed and nonsuppressed ion chromatography.

What is claimed is:  
     
         1 . A chemical analysis method for determining anions of interest in a sample to be analyzed, comprising the steps of: separating the anions of interest by anion exchange chromatography using a basic eluant to produce a stream of separated anions in the eluant; exchanging the cations of the stream of separated anions for hydrogen ion to produce a suppressed eluant stream; adding base to the suppressed eluant stream to produce a base treated suppressed eluant stream; mixing the base treated suppressed eluant stream; determining the electrical conductivity of the base treated suppressed eluant stream to determine the separated anions as a negative electrical conductivity response from a baseline response of the base treated suppressed eluant stream.  
     
     
         2 . The method of  claim 1 , wherein the noise level of the baseline response of the base treated suppressed eluant stream is less than one half the baseline noise level of a base treated suppressed eluant stream that is not mixed.  
     
     
         3 . The method of claims  1  and  2 , wherein the mixing of the base treated suppressed eluant stream is accomplished by flowing the base treated suppressed eluant stream through a helical tube containing a filament.  
     
     
         4 . The method of  claim 3 , wherein the tube comprises a base permeable membrane.  
     
     
         5 . The method of  claim 4 , wherein the base permeable membrane is a cation exchange membrane.  
     
     
         6 . The method of claims  1  and  2 , wherein the mixing of the base treated suppressed eluant stream is accomplished by flowing the base treated suppressed eluant stream through a tube containing particles.  
     
     
         7 . The method of  claim 6 , wherein the tube comprises a base permeable membrane.  
     
     
         8 . The method of  claim 7 , wherein the base permeable membrane is a cation exchange membrane.  
     
     
         9 . The method of claims  1  and  2 , wherein the mixing of the base treated suppressed eluant stream is accomplished by flowing the base treated suppressed eluant stream through a configured tube.  
     
     
         10 . The method of claims  1  and  2 , wherein the mixing of the base treated suppressed eluant stream is accomplished by flowing the base treated suppressed eluant stream through a channel partitioned from a source of base by a base permeable membrane, the channel containing a mixing element.  
     
     
         11 . The method of  claim 10 , wherein the mixing element is a screen.  
     
     
         12 . The method of  claim 10 , wherein the mixing element is a plurality of particles.  
     
     
         13 . The method of claims  10 ,  11  and  12 , wherein the base permeable planar membrane is a cation exchange membrane.  
     
     
         14 . The method of claims  1 - 13 , further comprising the step of determining the electrical conductivity of the suppressed eluant stream to determine the separated anions as a positive electrical conductivity response from a baseline response of the suppressed eluant stream.  
     
     
         15 . A chemical analysis method for determining cations of interest in a sample to be analyzed, comprising the steps of: separating the cations of interest by cation exchange chromatography using an acidic eluant to produce a stream of separated cations in the eluant; exchanging the anions of the stream of separated cations for hydroxide ion to produce a suppressed eluant stream; adding acid to the suppressed eluant stream to produce an acid treated suppressed eluant stream; mixing the acid treated suppressed eluant stream; determining the electrical conductivity of the acid treated suppressed eluant stream to determine the separated cations as a negative electrical conductivity response from a baseline response of the acid treated suppressed eluant stream.  
     
     
         16 . The method of  claim 15 , wherein the noise level of the baseline response of the acid treated suppressed eluant stream is less than one half the baseline noise level of an acid treated suppressed eluant stream that is not mixed.  
     
     
         17 . The method of claims  15  and  16 , wherein the mixing of the acid treated suppressed eluant stream is accomplished by flowing the acid treated suppressed eluant stream through a helical tube containing a filament.  
     
     
         18 . The method of  claim 17 , wherein the tube comprises an acid permeable membrane.  
     
     
         19 . The method of  claim 18 , wherein the acid permeable membrane is an anion exchange membrane.  
     
     
         20 . The method of claims  15  and  16 , wherein the mixing of the acid treated suppressed eluant stream is accomplished by flowing the acid treated suppressed eluant stream through a tube containing particles.  
     
     
         21 . The method of  claim 20 , wherein the tube comprises an acid permeable membrane.  
     
     
         22 . The method of  claim 21 , wherein the acid permeable membrane is an anion exchange membrane.  
     
     
         23 . The method of claims  15  and  16 , wherein the mixing of the acid treated suppressed eluant stream is accomplished by flowing the acid treated suppressed eluant stream through a configured tube.  
     
     
         24 . The method of claims  15  and  16 , wherein the mixing of the acid treated suppressed eluant stream is accomplished by flowing the acid treated suppressed eluant stream through a channel partitioned from a source of acid by an acid permeable membrane, the channel containing a mixing element.  
     
     
         25 . The method of  claim 24 , wherein the mixing element is a screen.  
     
     
         26 . The method of  claim 24 , wherein the mixing element is a plurality of particles.  
     
     
         27 . The method of claims  24 ,  25  and  26 , wherein the acid permeable planar membrane is an anion exchange membrane.  
     
     
         28 . The method of claims  15 - 27 , further comprising the step of determining the electrical conductivity of the suppressed eluant stream to determine the separated cations as a positive electrical conductivity response from a baseline response of the suppressed eluant stream.  
     
     
         29 . Apparatus for the chemical analysis of anions of interest in a sample to be analyzed, comprising: an anion exchange chromatography column; an ion chromatography suppressor in fluid communication with the anion exchange chromatography column; a base addition device in fluid communication with the ion chromatography suppressor; a mixer in fluid communication with the base addition device; an electrical conductivity detector in fluid communication with the mixer.  
     
     
         30 . The apparatus of  claim 29 , wherein the mixer is a helical tube containing a filament.  
     
     
         31 . The apparatus of  claim 30 , wherein the tube comprises a base permeable membrane.  
     
     
         32 . The apparatus of  claim 31 , wherein the base permeable membrane is a cation exchange membrane.  
     
     
         33 . The apparatus of  claim 29 , wherein the mixer is a tube containing a plurality of particles.  
     
     
         34 . The apparatus of  claim 33 , wherein the tube comprises a base permeable membrane.  
     
     
         35 . The apparatus of  claim 34 , wherein the base permeable membrane is a cation exchange membrane.  
     
     
         36 . The apparatus of  claim 29 , wherein the mixer is a configured tube.  
     
     
         37 . The apparatus of  claim 29 , wherein the mixer is a screen positioned in a flow channel adjacent a base permeable planar membrane.  
     
     
         38 . The apparatus of  claim 37 , wherein the base permeable planar membrane is a cation exchange membrane.  
     
     
         39 . The apparatus of  claim 29 , wherein the mixer is a plurality of particles in a flow channel adjacent a base permeable planar membrane.  
     
     
         40 . The apparatus of  claim 39 , wherein the base permeable planar membrane is a cation exchange membrane.  
     
     
         41 . The apparatus of claims  29 - 40 , further including an additional electrical conductivity detector in fluid communication with the ion chromatography suppressor and the base addition device.  
     
     
         42 . Apparatus for the chemical analysis of cations of interest in a sample to be analyzed, comprising: a cation exchange chromatography column; an ion chromatography suppressor in fluid communication with the anion exchange chromatography column; an acid addition device in fluid communication with the ion chromatography suppressor; a mixer in fluid communication with the acid addition device; an electrical conductivity detector in fluid communication with the mixer.  
     
     
         43 . The apparatus of  claim 42 , wherein the mixer is a helical tube containing a filament.  
     
     
         44 . The apparatus of  claim 43 , wherein the tube comprises an acid permeable membrane.  
     
     
         45 . The apparatus of  claim 44 , wherein the acid permeable membrane is an anion exchange membrane.  
     
     
         46 . The apparatus of  claim 42 , wherein the mixer is a tube containing a plurality of particles.  
     
     
         47 . The apparatus of  claim 46 , wherein the tube comprises an acid permeable membrane.  
     
     
         48 . The apparatus of  claim 47 , wherein the acid permeable membrane is an anion exchange membrane.  
     
     
         49 . The apparatus of  claim 42 , wherein the mixer is a configured tube.  
     
     
         50 . The apparatus of  claim 42 , wherein the mixer is a screen positioned in a flow channel adjacent an acid permeable planar membrane.  
     
     
         51 . The apparatus of  claim 50 , wherein the acid permeable planar membrane is an anion exchange membrane.  
     
     
         52 . The apparatus of  claim 42 , wherein the mixer is a plurality of particles in a flow channel adjacent an acid permeable planar membrane.  
     
     
         53 . The apparatus of  claim 52 , wherein the acid permeable planar membrane is an anion exchange membrane.  
     
     
         54 . The apparatus of claims  42 - 53 , further including an additional electrical conductivity detector in fluid communication with the ion chromatography suppressor and the acid addition device.